Impact of Secondary Sphere Hydrogen Bonds on O2 Reactivity within a Nonheme Iron Complex.

Abstract

A nonheme iron complex bearing the tris(6-phenylamino-pyridyl)methylamine (TPA^NHPh) ligand with appended hydrogen bond (H-bond) groups displays facile O₂ reactivity to form a monomeric Fe(III)OH complex, which can release •OH via rebound to a carbon radical. An analogous compound without H-bonds, based on tris(6-methylpyridyl)methylamine (TPA^Me), exhibits minimal O₂ reactivity, forming a Fe(III)₂(μ-O)(μ-OH) dimer, which also reacts with carbon-based radicals. The H-bonding system enables O₂ binding and activation at weakly reducing nonheme iron complexes, highlighting a cooperative role of secondary sphere units to facilitate reactions at atypical redox environments.